He was born in Newark, Essex, New Jersey on May 11th, 1888 as the only child of Leo David Greenfield (1863 - 1934), a furrier, and Blanche Strouse (1867-1936). Both his parents were born in New York and of German heritage.
William appears on the 1900 and 1910 census records living with his parents and grandmother Hannah Strouse in New York. By the time of the latter record he was described, like his father, as a furrier. He became vice president of Leo D. Greenfield & Co Inc., a manufacturer of fur garments for ladies.
Mr Greenfield was a frequent traveller, making annual trips to Europe where he would purchase fur pelts in Russia. He boarded the Titanic at Cherbourg with his mother Blanche Greenfield and they held ticket number PC 17759 which cost £63, 7s, 2d and occupied cabins D-10/12.
After the collision Mr Greenfield played cards in the first class smoking room with Alfred Nourney (Baron von Drachstedt) and Henry Blank. He, his mother and his card playing companions were rescued in Lifeboat 7, the first boat to leave the ship.
William rarely spoke about the Titanic disaster largely out of respect to his mother who was forever haunted by the screams of those who died in the icy waters. He later confided to family that it was not the sounds of humans perishing that haunted him most, but the dogs left behind who he heard barking and shrieking.
William continued to travel frequently on business, particularly to France, but also Britain, Belgium, Germany and the Netherlands. He was married in Manhattan on 7 October 1914 to Flora Stern (b. 11 November 1892), a New York resident born in Poland. They settled in Far Rockaway, Queens, New York and had two daughters: Anne (b. 1915) and Nell (b. 1919). He served during WWI following which he spent the 1920s and 1930s living in Queens before relocating to Manhattan by the time of the 1940s.
William died on November 12th, 1949 at the age of 61. He was buried at the Salem Field Cemetery in Brooklyn, New York where his parents were interred. His widow Flora later died in 1965.